I'm finally in the market for a receiver and am overwhelmed at the number of surround modes available from different receivers. I just wanted to see what formats do most people find they use/like the most. I know Dolby 5.1 is pretty much the standard for movies and I'm sure whatever receiver I choose will have it. But what about Dolby Digital EX or THX Surround EX. The receivers I'm looking at don't have those... So does that mean if I play Star wars TPM on an HK 520, there will be no back channel because the receiver doesn't have DD EX decoding? Why are there receivers with 7.1 pre-amp outs that don't have many formats that support the back channel? Is there a format that artifically creates the back 2 channels from a 5.1 source? Another question is has anyone listened to surrounds only and compared formats? I was wondering if people could actually tell a difference between matrix and discrete. I'm thinking of getting the HK 520 and using a 2ch amp for the surrounds but am worried that my DVDs will never use the back channels. Which would be a good reason to buy a 5.1 only receiver and save a bundle of money.